diff --git a/README.md b/README.md
index 30b65a2..eb2c508 100644
--- a/README.md
+++ b/README.md
@@ -534,7 +534,9 @@ Règles modélisées :
     dying/stabilized, conditions (noms + rounds_left), resources_left (+ `spell_slot_{level}`),
     weapon_broken/weapon_stolen, grappled_with, moved_this_turn, power_attack,
     name, level, size, dr {amount, bypass} ou None (C1), creature_type (C3),
-    bab (E1), initiative_mod (E2), casting_ability ou None pour non-jeteur
+    bab (E1), initiative_mod (E2) et initiative_total (U2 : total du jet
+    d'initiative courant = d20 + mod, 0 si pas encore de clé — invocation
+    fraîche), casting_ability ou None pour non-jeteur
     (E3), abilities {str/dex/con/int/wis/cha: score brut} (Medium), skills
     {nom: {rank, class_skill, armor_penalty}} uniquement rank > 0 (Medium),
     metamagic_feats (tuple trié), weapon_damage {weapon_id: dégâts courants},
@@ -563,6 +565,9 @@ Règles modélisées :
     flanking, movement_cost_ft, target_threatens_me, enemies_threatening_me.
   - Top-level : round, acting_combatant, combatants, pairs, terrain, elevation,
     threatened (grille bool des cases menacées par les ennemis),
+    initiative_order (U2 : tuple d'ids dans l'ordre d'initiative du round
+    courant — le premier est le prochain à agir ; les invocations héritent de la
+    case de leur conjurateur),
     terrain_semantics (un dict par type de terrain : type, move_cost,
     blocks_los, cover, cover_bonus), condition_definitions (C2 : tuple trié de (nom,
     {mods, flags, speed_mult, miss_chance}) — définitions complètes des 23
diff --git a/src/pf1e_simulator/combat.py b/src/pf1e_simulator/combat.py
index fda0bc5..f946a73 100644
--- a/src/pf1e_simulator/combat.py
+++ b/src/pf1e_simulator/combat.py
@@ -448,7 +448,9 @@ class Observation:
     on the map (sorted by type for determinism), carrying
     ``{type, move_cost, blocks_los, cover}`` — derived from
     ``grid.terrain_at((r, c))`` over the entire map (the Grid does not expose
-    ``MapSpec.legend``).
+    ``MapSpec.legend``). ``initiative_order`` lists the combatant ids in the
+    current round's initiative order (``_build_round_order()``, read-only,
+    no RNG): the first entry acts next this round.
     """
 
     round: int
@@ -460,6 +462,7 @@ class Observation:
     threatened: tuple[tuple[bool, ...], ...] = ()
     terrain_semantics: tuple[dict[str, object], ...] = ()
     condition_definitions: tuple[tuple[str, dict[str, object]], ...] = ()
+    initiative_order: tuple[str, ...] = ()
 
     def to_dict(self) -> dict[str, object]:
         """Return a JSON-serializable dict with the pinned top-level keys."""
@@ -473,6 +476,7 @@ class Observation:
             "threatened": self.threatened,
             "terrain_semantics": self.terrain_semantics,
             "condition_definitions": self.condition_definitions,
+            "initiative_order": self.initiative_order,
         }
 
 
@@ -710,6 +714,9 @@ class CombatEngine:
             (name, _condition_definition_dict(cond))
             for name, cond in sorted(CONDITIONS_BY_NAME.items())
         )
+        initiative_order = tuple(
+            s.combatant.id for s in self._build_round_order()
+        )
         return Observation(
             round=self._current_round,
             acting_combatant=acting_index,
@@ -720,6 +727,7 @@ class CombatEngine:
             threatened=threatened,
             terrain_semantics=terrain_semantics,
             condition_definitions=condition_definitions,
+            initiative_order=initiative_order,
         )
 
     def _threat_grid(self, state: CombatantState) -> tuple[tuple[bool, ...], ...]:
@@ -809,6 +817,9 @@ class CombatEngine:
             "creature_type": state.combatant.creature_type,
             "bab": state.combatant.bab,
             "initiative_mod": state.combatant.initiative_mod,
+            "initiative_total": self._initiative_keys.get(
+                state.combatant.id, (0, 0, -999)
+            )[0],
             "casting_ability": (
                 state.combatant.casting_ability if state.combatant.spells else None
             ),
diff --git a/tests/test_initiative_observation.py b/tests/test_initiative_observation.py
new file mode 100644
index 0000000..f7f7944
--- /dev/null
+++ b/tests/test_initiative_observation.py
@@ -0,0 +1,151 @@
+"""Initiative exposure in the Observation (Package U2).
+
+Top-level ``initiative_order`` (ids in the current round's initiative order,
+from ``_build_round_order()``, read-only, no RNG) and per-combatant additive
+key ``initiative_total`` (the d20 roll + initiative_mod from ``_initiative_keys``,
+0 when no key exists yet, e.g. fresh summons).
+"""
+from __future__ import annotations
+
+import json
+
+from pf1e_simulator.combat import CombatantState, CombatEngine
+from pf1e_simulator.dice import parse_dice
+from pf1e_simulator.models import (
+    AbilityScores,
+    ACProfile,
+    AttackSpec,
+    Combatant,
+    DamageComponent,
+    Saves,
+)
+from pf1e_simulator.rng import ScriptedRng
+from tests.test_observation_enriched import _snapshot, make_grid, make_state
+
+
+def _combatant(id_: str, *, initiative_mod: int = 0) -> Combatant:
+    return Combatant(
+        id=id_,
+        name=id_,
+        level=1,
+        abilities=AbilityScores(
+            str_score=10, dex_score=10, con_score=10,
+            int_score=10, wis_score=10, cha_score=10,
+        ),
+        ac=ACProfile(total=10, touch=10, flat_footed=10),
+        bab=1,
+        initiative_mod=initiative_mod,
+        speed_land_ft=30,
+        hp_max=100,
+        saves=Saves(fort=0, ref=0, will=0),
+        attacks=[
+            AttackSpec(
+                id=f"{id_}-sword",
+                name="short sword",
+                kind="melee",
+                attack_bonus=1,
+                damage=[
+                    DamageComponent(formula=parse_dice("1d6"), types=["slashing"])
+                ],
+            )
+        ],
+    )
+
+
+def _engine(rng: list[int], states: list[CombatantState]) -> CombatEngine:
+    return CombatEngine(ScriptedRng(rng), make_grid(), states)
+
+
+def _duel() -> CombatEngine:
+    """hero (mod +5, d20=4 → total 9) vs foe (mod 0, d20=10 → total 10)."""
+    hero = make_state(_combatant("hero", initiative_mod=5), "players", (0, 0))
+    foe = make_state(_combatant("foe"), "monsters", (0, 3))
+    return _engine([4, 10], [hero, foe])
+
+
+# ── (a) initiative_order == _build_round_order ids, descending key ───────────
+
+
+def test_initiative_order_matches_round_order() -> None:
+    eng = _duel()
+    eng._roll_initiative()
+    obs = _snapshot(eng, eng._states[0])
+
+    order = obs["initiative_order"]
+    assert isinstance(order, tuple)
+    assert order == tuple(s.combatant.id for s in eng._build_round_order())
+    # foe total 10 > hero total 9 → foe acts first despite later deployment.
+    assert order == ("foe", "hero")
+
+
+def test_initiative_order_sorts_descending_by_full_key() -> None:
+    a = make_state(_combatant("a", initiative_mod=2), "players", (0, 0))
+    b = make_state(_combatant("b", initiative_mod=5), "players", (0, 1))
+    c = make_state(_combatant("c", initiative_mod=5), "monsters", (0, 2))
+    # keys (total, mod, index): a=(5,2,0), b=(10,5,1), c=(10,5,2) sorted
+    # descending → full b/c tie breaks on the index component (c first).
+    eng = _engine([3, 5, 5], [a, b, c])
+    eng._roll_initiative()
+    obs = _snapshot(eng, a)
+    assert obs["initiative_order"] == ("c", "b", "a")
+
+
+# ── (b) initiative_total == _initiative_keys total == logged d20+mod ─────────
+
+
+def test_initiative_total_matches_key_and_log() -> None:
+    eng = _duel()
+    eng._roll_initiative()
+    obs = _snapshot(eng, eng._states[0])
+
+    totals = {c["id"]: c["initiative_total"] for c in obs["combatants"]}
+    assert totals == {"hero": 9, "foe": 10}
+    for cid, total in totals.items():
+        key_total, _mod, _index = eng._initiative_keys[cid]
+        assert total == key_total
+    # The snapshot agrees with the pinned initiative log lines.
+    assert "initiative: hero d20=4+5=9" in eng._transcript
+    assert "initiative: foe d20=10+0=10" in eng._transcript
+    # initiative_mod stays as the combatant's static modifier.
+    mods = {c["id"]: c["initiative_mod"] for c in obs["combatants"]}
+    assert mods == {"hero": 5, "foe": 0}
+
+
+# ── (c) summons / states without an initiative key → total 0, no crash ──────
+
+
+def test_summon_without_key_has_zero_total_and_inherits_order() -> None:
+    eng = _duel()
+    eng._roll_initiative()
+    summon = make_state(_combatant("serpent"), "players", (0, 2))
+    summon.summon_caster_id = "hero"
+    summon.summon_duration = 5
+    eng._states.append(summon)
+
+    obs = _snapshot(eng, eng._states[0])
+    totals = {c["id"]: c["initiative_total"] for c in obs["combatants"]}
+    assert totals["serpent"] == 0  # no own key yet — neutral default
+    # The summon inherits the caster's key → acts right after hero (total 9).
+    assert obs["initiative_order"] == ("foe", "hero", "serpent")
+
+
+def test_snapshot_before_initiative_roll_is_safe() -> None:
+    eng = _duel()  # _roll_initiative never called: no keys at all
+    obs = _snapshot(eng, eng._states[0])
+    for combatant in obs["combatants"]:
+        assert combatant["initiative_total"] == 0
+    assert isinstance(obs["initiative_order"], tuple)
+    json.dumps(obs)  # must not raise
+
+
+# ── (d) to_dict JSON-serializable and includes initiative_order ──────────────
+
+
+def test_to_dict_includes_initiative_order_and_is_json_safe() -> None:
+    eng = _duel()
+    eng._roll_initiative()
+    data = eng._build_observation(eng._states[0]).to_dict()
+
+    assert "initiative_order" in data
+    parsed = json.loads(json.dumps(data))
+    assert parsed["initiative_order"] == ["foe", "hero"]
diff --git a/tests/test_observation_enriched.py b/tests/test_observation_enriched.py
index 7da0338..1b8bd59 100644
--- a/tests/test_observation_enriched.py
+++ b/tests/test_observation_enriched.py
@@ -1057,6 +1057,7 @@ def test_observation_enriched_e5_existing_keys_preserved() -> None:
         "threatened",
         "terrain_semantics",
         "condition_definitions",
+        "initiative_order",
     }
     # combatants / pairs untouched by E5
     assert len(obs["combatants"]) == 2